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PSU tests OK but when changing to another one, PC boots

itnifl
itnifl asked
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Last Modified: 2013-12-01
My PC stopped working the other day. Couldn't turn it on anymore. There was a green light that turned on, on the motherboard, other then that, nothing. No fans, no beeps, nothing on the display. Tested the PSU with a PSU tester, it tested OK. Every voltage and measurement within its range. Still when changing to a different PSU, everything boots and starts as normal. Any known possible explanations to this?
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Check whether your monitor is attached properly to your display card.
Did your whether processor is attached properly
itniflProgrammer

Author

Commented:
If any of those were not attached properly, I would get the same result with both PSU's. Both PSU's test fine, but computer does not boot with the old one. Re-tested several times.
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Gary CaseRetired
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Most Valuable Expert 2013
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Commented:
As willcomp noted, this simply means the voltages are okay, but the current capacity of the old PSU has deteriorated to where it can no longer power your system.    I'd simply toss the old power supply.    Just be glad it was such a simple problem :-)
JohnBusiness Consultant (Owner)
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Expert of the Year 2018

Commented:
These are pretty much the same answers as I gave earlier when I said (a) a voltmeter does not load a circuit and (b) the problem supply was not able to provide the required current.

... Thinkpads_User

Commented:
@thinkpads_user - note times on our responses. I was typing when you posted your answer.
CERTIFIED EXPERT
Distinguished Expert 2019

Commented:
when i test a PS, i always apply a load to the different voltage rails : 12 V, 5 V, and 3.3 V
i made a rig of car lamps for 12 V loads, and use resistor chains for the others.

another cause that it does not start, can be bulging or leaking capacitors inside the PS
aften you have to repalce only a couple to get it working again
here's how they look :
c
itniflProgrammer

Author

Commented:
Thanks guys! This is great. i'll just toss the old one and use the new one. I don't want to spend time trying to repair it. I am not familiar with such work, would end up spending more time then interests me, and therefore just opt for the simplest solution :)
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
@itnifl - Thanks for the update. In this case, replacement is probably the right answer.

.... Thinkpads_User
CERTIFIED EXPERT
Distinguished Expert 2019

Commented:
nearly all bad PS's  i had in have been repaired

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